A Universe of Universes

By George Johnson

Published: July 27, 1997

The Life of the Cosmos

By Lee Smolin.

358 pp. New York: Oxford University Press. $30.

When it comes to making sense of how life unfolded on this planet, the theory of evolution is almost impossible to resist. Random mutations generate a menagerie of competing creatures that are tested by the demands of the environment. The fittest are more likely to reproduce and multiply. And so steadily, over the millenniums, an exquisitely adapted ecosystem has emerged. It is hard to find another theory, anywhere in science, that has such explanatory power.

The closest might be the Big Bang. But the Big Bang theory has an enormous shortcoming: it does not provide a satisfying account for why the flying debris of the primordial blast congealed into stars and galaxies, and galaxies of galaxies -- a hierarchy of structure. It is vastly more likely that the universe would have turned out to be utterly random, a featureless fog.

More miraculous still is that the Big Bang seems to have produced a universe perfectly designed to support life. It's often argued -- as the cosmologist Lee Smolin does in ''The Life of the Cosmos'' -- that if gravity or electromagnetism were a little stronger or a little weaker, or if the nuclear forces were not precisely as they are, there would be no stars. And without stars, which cook hydrogen and helium into carbon and other complex atoms, there would be no chemistry, no biology, no complexity, no life. The question -- as Smolin, a professor at the Center for Gravitational Physics and Geometry at Pennsylvania State University, puts it -- is ''Why is the universe so interesting?'' Seeking an answer, he takes a dizzying intellectual leap. Since evolution so successfully explains why the biosphere is the way it is, why not apply the theory to the whole of creation? The universe is perfectly tuned to allow for life because it evolved that way.

But an evolving universe would have to compete with other universes, right? So we are off on a wild cosmological adventure. When a very large star collapses of its own dead weight, it forms a black hole, a kind of tear in the fabric of space-time. Weird as it is, this much is mainstream cosmology. Smolin applies another twist: out the other end of every black hole pops a new universe with slightly different physical laws. If that universe, burgeoning from its own Big Bang, can also make stars massive enough to collapse into black holes, it will produce more offspring. Indeed, our own universe emerged, Smolin speculates, through a black hole in some other universe. Universes multiply like rabbits. The result is a universe of universes, dominated by the ones that are fittest -- those best equipped to make the stars and black holes that allow them to reproduce. These are also the universes capable of supporting complex phenomena like life.

It's great fun to see the implications of this fantastic idea laid out by so original a thinker. But in the end I wasn't convinced that his is a verifiable scientific theory. Smolin says it can be tested indirectly. Suppose we examine all the physical parameters that define our world -- the charge of the electron, for example, or the mass of the top quark -- and find that slightly altering any of them would result in a universe with fewer black holes. This, he proposes, would strongly support the notion that our own universe was the result of evolutionary fine-tuning. Well, maybe. There is probably enough wiggle room in the interpretation of such thought experiments for other cosmologists, in the grip of their own visions, to propose equally plausible explanations.

I was far more impressed with the insightful account Smolin gives of the ambitious effort of physicists to come up with a theory of what they call quantum cosmology -- one that would combine science's picture of the very small, quantum mechanics, with its picture of the very large, general relativity. Right now the theories, so different in style, seem immiscible. Before we can meld them, Smolin says, we must answer this question: ''How can we, who live in the world, construct a complete and objective description of the universe as a whole?'' We can't step outside the universe; we are inevitably part of what we are trying to describe. But though it is nonsense to talk about something being outside the universe, science does it all the time. Before quantum mechanics and relativity, physicists conceived of the universe as matter moving around inside a pre-existing trellis of space and time. Where did space and time come from? They had to be taken as givens, articles of faith, something outside the system.

Einstein showed how time and space can be thought of not as mysterious essences but simply as relationships among the stuff of the world. Even so, science's picture of the universe is still far from self-contained. Modern physics talks about the laws of the universe as if they were written on a tablet on some ethereal plane.

But couldn't the laws, too, be shown to have arisen from inside? Smolin argues that the laws evolved. But you don't have to buy this in order to appreciate the beauty of his more general idea of a universe so complete that even its mathematical rule book exists somehow within it.

The spirit of this notion underlies a maddeningly abstract idea called gauge symmetry. As Smolin clearly explains it, qualities like the charge of an electron are not absolute, inherent properties. They emerge from the interactions among all the particles in the universe. I've read every popular and semipopular account of gauge symmetry I could find, and they all stumble in trying to make sense of this difficult idea. Finally, in this book, I started to get it.

Despite some creative punctuation and a lot of typographical errors, most of the book is very lucid. It clouds only toward the end, when Smolin tries to describe how space and time might emerge from the writhing of mathematical abstractions called knots. But still his overarching theme comes through. In an ultimate theory, everything must emerge from the interaction of simple parts. It is cheating to invoke laws that lie somewhere beyond the horizon.

But isn't it also cheating to posit a multitude of ever-multiplying universes, each forever sealed off from our own on the other side of black holes? If it takes that much invisible apparatus to account for the complexity of the universe, maybe cosmologists are on the wrong track. Smolin makes some of the strongest arguments I've seen that understanding the universe will require a serious search for some kind of laws of complexity. But it is still possible that we are living inside a small pocket of order, a backwater in a universe overwhelmed by randomness.

George Johnson, the author of ''Fire in the Mind: Science, Faith, and the Search for Order,'' is writing a biography of the physicist Murray Gell-Mann.